Difference between revisions of "BASH/C3/More-on-functions/English"

• To pass an argument to a function
• Define local variable within a function and
• Define global variable in a function
• With the help of some examples

If not, for relevant tutorials please visit our website which is as shown,(http://www.spoken-tutorial.org)

System requirements

• Ubuntu Linux 12.04 Operating System and
• GNU BASH version 4.2

Please note, GNU Bash version 4 or above is recommended to practice this tutorial.

{

Open curly bracket opens the function definition.

$2 is the second postional parameter

say_welcome "Bash" "learning"

The syntax is, function name i.e. say welcome

...followed by the arguments within double quotes, i.e. Bash and learning.

say_welcome "functions in" "Bash"

So, I have

say_welcome space within double quote functions in space and within double quote Bash.

chmod +x function_parameters.sh>>Press Enter

Press Enter.

./function_parameters.sh>>Press Enter

Press Enter.

[Output]

Welcome to Bash learning

Welcome to functions in Bash

Dollar 1($1) was substituted by the string Bash and Dollar 2($2) with learning.

Then again, Dollar 1($1) was substituted by functions in and Dollar 2($2) with Bash.

Local and Global variables in functions

• Local variable:
• It's value will be valid within the function in which it is defined.
• Local variables are declared using keyword 'local'.

Local and Global variables in functions

• The value of a global variable can be accessed throughout a Bash script.

#Local variable

Which means, its value will be valid within the function say_hello only.

# Global variable

So, the variable last_name can be accessed throughout the script.

Highlight }

• first_name,
• middle_name and
• last_name

After this, we close this function.

#global variable

So, its value will be global throughout the script.

We pass two arguments to this function call, namely, “Pratik” and “Patil”.

echo "My first name is: $first_name"

echo "My middle name is: $middle_name"

echo "My last name is: $last_name"

• $first_name,
• $middle_name and
• $last_name

chmod +x function_local.sh>>Press Enter

Press Enter.

dot slash function underscore local dot sh

Press Enter.

[Output]

Hello Pratik K Patil

Here, the variable first_name that contains value “Pratik” is local.

Which means the value is limited to the function.

[Output]

My first name is:

My middle name is: k

My last name is: Patil

This is because the value of first_name is local to the function.

And it is not available outside the function.

middle_name and last_name are printed as they are global variables.

Let us now summarise.

Summary

• To pass arguments to a function
• To declare Local variable in a function
• To declare Global variable in a function
• with the help of a few examples

Assignment

Write a program,

• Where the function accepts two arguments.
• The function should multiply the two arguments.
• Make 3 function calls with arguments (1, 2), (2, 3) and (3, 4)

http://spoken-tutorial.org /What\_is\_a\_Spoken\_Tutorial

About the Spoken Tutorial Project

It summarises the Spoken Tutorial project.

If you do not have good bandwidth, you can download and watch it.

Spoken Tutorial Workshops

• Conducts workshops using spoken tutorials
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Acknowledgement

It is supported by the National Mission on Education through ICT, MHRD, Government of India.

More information on this Mission is available at:

http://spoken-tutorial.org\NMEICT-Intro

This is Ashwini Patil from IIT Bombay signing off.

Thank you for joining.